I have my mini and display set to sleep after 10 minutes of inactivity. Quite a few times I have noticed it does not do so.

I had Mail, iCal, Safari and iPhoto open just this last time.

I have Mail set to check for new messages every minute. I'm thinking this is the problem. I just set it to check manually (or I guess anything above 10 minutes would work in my case). I hope this solves the problem.

Any other suggestions as to what may be causing this?
I have an Apple wired keyboard and Logitech wired optical mouse. There is no chance that the mouse got moved.

I have Mail set to check for new messages every minute. I'm thinking this is the problem. I just set it to check manually (or I guess anything above 10 minutes would work in my case). I hope this solves the problem.

I bet that solves it. Why not set it to check for mail every hour to give yourself some time. You can check it manually any old time._________________My Setup

Bandit Bill, I have my mail set to check every 3 minutes, and mine goes to sleep fine. What I found keeping mine awake was the new HP Deskjet 3740 printer that I just bought. After unplugging it, now it goes to sleep just like it did before. At least I think this is what's going on, because it worked perfectly before.